1. Field of the Invention
The present invention relates to a blue electroluminescent polymer and an organic electroluminescent device using the same, and more particularly, to a blue electroluminescent polymer having a phenoxazine-based unit in a polyarylene backbone and an organic electroluminescent device having improved luminous efficiency and color purity by using the blue electroluminescent polymer as a light-emitting component.
2. Description of the Related Art
Organic electroluminescent devices are active matrix emission type display devices in which, when an electrical current is applied to a fluorescent or phosphorescent organic compound layer (hereinafter, referred to as an organic layer), electrons and holes are combined in the organic layer to emit light. Organic electroluminescent devices are light and comprise simple components and thus may be manufactured in a simplified process, and also have a wide view angle and high image quality. Further, they can display high quality moving pictures, have high color purity, and can be suitably used for portable electronic devices with low power consumption and low driving voltage.
Such organic electroluminescent devices are classified into low molecular weight organic electroluminescent devices and high molecular weight organic electroluminescent devices depending on a molecular weight of a material used in an organic layer.
In low molecular weight organic electroluminescent devices, an organic layer can be formed by vacuum deposition, the light-emitting materials can be easily purified to a high degree, and color pixels can be easily obtained. For practical applications of the low molecular weight organic electroluminescent devices, however, the quantum efficiency and color purity must be further improved, and crystallization of thin layers must be prevented.
In high molecular weight organic electroluminescent devices, an organic layer can be easily formed by spin coating or printing, so that such polymer organic electroluminescent devices can be manufactured in a simplified manner at low costs. Also, the organic layer exhibits good mechanical properties.
However, high molecular weight organic electroluminescent devices have low color purity and a short lifetime. To overcome these problems. U.S. Pat. No. 6,169,163 describes a method of copolymerizing fluorene-containing polymers to improve electroluminescent characteristics of high molecular weight organic electroluminescent devices. However, the achieved improvement is not satisfactory.
Also, Korean Laid-Open Patent Publication No. 2003-0097658 describes a blue electroluminescent polymer having a phenoxazine unit in a polyarylene backbone and an organic electroluminescent device comprising an organic layer containing the blue electroluminescent polymer. However, the color purity and lifetime of the device should be increased.
Thus, there is an increasing need to develop a phenoxazine monomer in order to improve the color purity while maintaining the lifetime of the device.